If it is as you describe, $1500 is a steal. The 320 you mention sounds like it was either in there at one time or intended to be swapped in because the Buick had a straight 8 originally. While parts might be a little tougher to score than say similar parts for a Ford, they are still out there. You could join some Buick forums and get all the help and parts you need there too.

I think you will kick yourself if you pass this one up.

Don